The objective of this study is to understand the basic physiology of hypothalamic-pituitary-gonadal interaction. The focus of our current studies if the interaction between hypothalamus and pituitary gland, examining the normal patterns of IHRH-IH-FSH release during the normal menstrual cycle, and on the interactions between the theca and granulosa cell compartments of the ovary and how this interfaces with pituitary function. During the past year three projects were completed. First, the gonadotropin secretory pattern in normal women throughout the menstrual cycle has been established. Pulse secretory frequency increases during the follicular phase and decreases during the luteal phase of the cycle. Pulse amplitude is constant except at the midcycle surge at which time it increases dramatically. Progestins have been shown capable of slowing pulse frequency. Second, it was shown that granulosa cell products, estradiol and estrone, can markedly alter the activity of several theca cell steroid biosynthetic enzymes. This provides a biochemical mechanism for theca assessment of follicular maturation. Third, we have shown the testosterone production rates in men with isolated FSH elevations are approximately half normal, suggesting that the FSH elevation follows from androgen deficiency rather than from an insufficiency of the hypothetical tubular hormone, inhibin.